Control device



July 21, 1931.

R. C. HITCHCOCK CONTROL DEVICE Filed Jurie 22, 1927 ATTORNEY PatentedJuly 21, 1931 RICHARD C. HITCHCOCK, OF WILKINSBURG, PENNSYLVANIA,ASSIGNOR- T0 WESTING- HOUSE ELECTRIC & MANUFACTURING OOBEPANY, A

VANIA CORPORATION OF PENNSYL- C'ONTROL DEVICE Application filed June 22,

My invention relates to control devices, and it has particular relationto devices intended to control the frequency of an oscillation generatorcomprising a thermionic tube.

One object of my invention is to provide a frequency-control device thatshall be capable of controlling more power than similar devices known tothe prior art.

Another object of my invention is to vide a frequency-control device ofthe piezoelectric-crystal type that may be accurately maintained at apredetermined temperature, irrespective of the amount of power beingcontrolled thereby.

Another object of my invention is to provide apiezo-electric-crystal-holding device that may be entirely submerged ina cooling liquid, if desirable.

Another and more specific object of my invention is to provide a piezoelectriocrystalholding device that shall be rugged in con struction, andone in which the spacing of the electrodes shall be relativelypermanent, irrespective of the position in which the device is mounted,or the vibration to which it is subjected while in use.

When piezo-electric crystals are utilized to control the frequency ofoscillations generated by a thermionic tube, in the manner now wellknown to those skilled in the art, it has been found that numerousfactors combine to prevent the maintenance of a constant, unvaryingfrequency. As the amount of power controlled increases, the voltage fedback through the controlled tube also increases, thus causing thecrystal to physically vibrate with greater amplitude and to accordinglygenerate a greater amount of heat. The heat generated, both by reason ofthe physical vibration of the crystal, and by the dielectric hysteresislosses therein causes the actual vibration frequency to change to a verymarked degree unless it is dissipated by efficient cooling devices.

The effect of temperature upon crystal fre quency was appreciated byearlier workers in the art, as evidenced by Patent No. 1,609,7 i4l,issued to A. M. Trogner on Dec. 7, 1926, and by an application in thename of D. G. Little, Serial No. 78,115, filed December 29, 1925, and

pro-

1927. Serial No. 200,722.

assigned to lVestinghouse Electric & Manufacturing Company.

In the latter application, it is shown that the temperature of acontrol-crystal must be maintained reasonably constant, a chamberprovided with a heating coil and a thermostat being disclosed for thispurpose.

My present invention is in the nature of an improvement over theinvention disclosed in the application of D. G. Little, being directedtoward instrumentalities for more efiiciently conducting away the heatgenerated by a piezo-electric crystal, in order that the oscillationfrequency thereof may be maintained accurately fixed.

To accomplish the purpose of my invention, 1 preferably mount thecrystal-section in an evacuated container, or in a container filled withan inert gas at a very low pressure. The crystal is held in contact witha wall-portion of the container that is both electrically andheat-conducting, and the said wall portion, or the entire container, maybe submerged in a body of insulating cooling liquid.

In some instances, when extremely accurate temperature control isdesirable, or when, in order to influence the oscillation frequency, itis desired to maintain the crystal at a temperature higher than thatwhich it would naturally assume in operation, the insulating liquid maybe provided with a heating coil controlled by a thermostat.

Among the novel features of my invention are those particularly setforth in the appended claims. The invention in its generic aspect,however, as well as further objects and advantages thereof, will best beunderstood by reference to the following descrip tion taken inconnection with the accompanying drawing, the single figure of which isa view of a preferred modification.

Referring to the drawing, the preferred modification of my inventioncomprises a container 1, preferably made of a translucent or transparentinsulating material, such as glass, to one end of which is sealed ametallic cup 2, preferably made of copper, or other material which hasgood thermal conductivity. The end of the container opposite themetallic cup is provided with a re-entrant portion 8, through whichextends a leadingin conductor t.

A relatively thick metallic electrode-device 5 rests upon the bottom ofthe metallic cup 2, being maintained in thermal and electrical contacttherewith by brazing or soldering.

A second electrode device 6 is supported from the first electrode device5, at a plurality of points around the circumference thereof', by meansof insulating spaced elements 7 which encircle a plurality of studs 8threadedly connected to the electrode 5. Theupper ends of the studs 8,at the points where they extend through openings in the upper electrode,are surrounded by insulating sleeves 10. 'l he electrode assemblyrigidly held together by a plurality of lock nuts ll threaded on theupper ends of the studs, each of these nuts transmitting pressure to theinsulating sleeves associated w'th the respective studs by means of sprig washers 12, or the like. I have found it preferable to use only threeassembly study, since, b" using a three-point support for the upper-rode, inequalities in the height of the collars 7 will not introducewarping strains.

A connecting element 13 is atlixed to, and supported by, the upperelectrode 6 and is connected, by a flexible conductor 14-, to theleading-in wire a.

A flexible conductor 15 is soldered or otherwise affixed to the metalliccup 2, in order that the cup may be electrically connected to theappropriate element of a thermionic tube when the device is utilized tocontrol the frequency of oscillations generated thereby.

The space between the electrodes 5 and 6 is determined by the thicknessof the insulating collars 7, and varies according to the thickness of acrystal-section 1.6 which is maintained intermediate the saidelectrodes, and is prevented from dropping out by the said collars. Thisspace is so chosen that the upper electrode is not in electrical contactwith the crystal in is a very slight distance above it, the saiddistance preferably being a non-integral multiple of the wave length, inair, of the crystal-frequency.

In order that sparking, if it occurs, shall not cause corrosion of themetallic portions of the device, it is preferable, after exhausting thecontainer, to admit thereto a small amount of inert gas, such as neon orargon, at a pressure of about 5 to 15 millimeters of mercury.

hen employing a device constructed according to my invention forfrequency control, the entire container may be, if desirable, immersedin a body of insulating liquid. It is also feasible to merely insert thelower metallic portion of the device into an inert body of coolingliquid, or a suitable receptacle may be provided through which thecooling liquid may be circulated in contact with the said metal portion.in certain instances, I have found it desirable to provide the liquidwith a heating coil and to maintain the temperature constant byutilizing a thermostat to control the potential applied to the coil.

I have found that, when using a device constructed according to myinvention for the control of the frequency of high-powderedoscillator-tubes, there is very little likelihood of the temperaturerising sutliciently high to cause crystal breakage. 15y reason of thefact that the crystal is in intimate contact with the metallic cup, andthe said cup being capable of being etliciently cooled, I am enabled tomaintain the crystal temperature substantially constant, irrespective ofthe amount of power l eing controlled thereby.

/Vhen oscillating properly, the crystal is surrounded by a visible glowwhich results from ionization of that portion of the gas in theimmediate vicinity thereof. By reason of the fact that the upper portionof the container is either translucent or transparent, the attendantcan, at all times, satisfy himself by inspecting the glow that thecrystalv properly oscillating, and that the out put frequency of thethermionic device as sociated' therewith is that frequency to which thecrystal naturally oscillates.

The device may be subjected: to a reason able amount of rough treatmentshort of causing actual breakage thereof, with the full assurance thatthe initial spacing be tween the electrodes will. not change. This adecided advantage, inasmuch asthe device will often be carelesslyhandled by the attendant in charge of the radio transmitting station inwhich it is being used.

Although I have illustrated and described a specific embodiment of myinvention, 1 am fully aware of the fact that many modifications thereofare possible. My invention, herefore, is not to be limited eXcept in sofar as necessitated by the prior art and by the spirit of the appendedclaims.

I claim as my invention:

1. As an article of manufacture, a piezoelectric-crystal-holding devicecomprising an evacuated container having a transparent insulatingportion, a conductor extending through a wall of said transparentportion, a metallic base portion, an elecrodc, means independent of thecrystal for insulatingly supporting said electrode from said baseportion, and a connection between said electrode and said conductor.

2. In combination, an evacuated container having anelectrically-conducting and heatconducting portion, a massive electrodesup ported in contact with said portion, an electrode insulatinglysupported from said first electrode, a conductor aflixed to said secondelectrode and extending to the exterior of said container and apiezo-electric crystal intermediate said electrodes.

3. In combination, an evacuated container having anelectrically-conducting and heat conducting portion, a translucentinsulating portion, an electrode in said container in coir tact withsaid heat-conducting portion, a second electrode in said container,means for supporting said second electrode in a fixed position relativeto said first electrode and for insulating it therefrom, a conductoratfixed to said second electrode and extending through said insulatingportion and a piezoelectric crystal intermediate said electrodes.

4. In combination, an evacuated container having anelectrically-conducting and heatconducting portion, a massive electrodein said container in contact with said portion, a second electrode andmeans for insulatingly supporting said second electrode from the massiveelectrode in fixed relation thereto.

5. A piezo-electric crystal holder comprising an evacuated containerhaving an upper transparent portion, a lower heat-conducting andelectrically-conducting portion supporting said first-named portion andadapted to be cooled by external agencies, and an electrode insulatinglysupported from said lowor portion interiorly of said container to definea space wherein a piezoelectric crystal may be disposed.

6. A pieZo-electric crystal holder comprising an evacuated containerhaving an upper transparent portion, a lower heat-conducting andelectrically conducting portion supporting said first-named portion, anelectrode in contact with said lower portion interiorly of saidcontainer, a second electrode disposed in parallel relation to saidfirst-mentioned electrode, and a plurality of insulating devices forsupporting said second electrode from said first electrode.

7. A piezo-electric crystal holder comprising an evacuated containerhaving an electrically-conducting and heat-conducting portion, anelectrode in said container in contact with said heat-conductingportion, a second electrode in said container, means for supporting saidsecond electrode in substantial- 1y parallel relation to said firstelectrode and.

for insulating it therefrom, and resilient means tending to urge saidelectrodes toward each other.

8. A piezo-electric crystal holder comprising an evacuated containerhaving an electrically-conducting and heat-conducting portion, anelectrode in said container in contact with said heat-conductingportion, a second electrode in said container, and three insulatingsupporting elements for retaining said second electrode in substantiallyparallel relation to said first electrode to define a crystalreceivingspace, the said supporting elements being disposed at the apices of atriangle.

9. A piezo-electric crystal holder comprising a container having anelectrically-conducting and heat-conducting portion and a transparentinsulating portion, a massive electrode in said container in contactwith said heat-conducting portion, a second electrode in said container,means for supporting said second electrode in substantially parallelrelation to said first electrode and for insulating it therefrom, aconductor affixed to said second electrode and extending through saidtransparent portion to the exterior of said container, and rarefied gasin said container that is inert with respect to said electrodes and theheat-conducting portion of the container.

In testimony whereof, I have. hereunto subscribed my name this 13th dayof June,

RICHARD C. HITGHCOOK.

